This invention pertains to insulating flanges for pipelines. More particularly, it relates to a high pressure insulating flange-like coupling made by winding plastic impregnated fiber glass on a spool formed by supporting two spaced apart metal half flanges on a nonmetallic cylinder.
In the pipeline industry, insulating couplings or flanges are used for many purposes. For example, the design, construction, operation, maintenance and salvage of metal pipelines, including flowlines and well casing, depend in part on the control of external corrosion of such tubular goods. External corrosion is caused when a pipeline is made up of metal tubular goods having different surface potentials either due to dissimilarity in metal composition or in surface newness or preparation, or when electrically connected corrosive metal tubular goods traverse different electrolytic environments, or when the electrically connected metal tubular goods pick up stray or induced electrical currents which are later discharged into the soil or water around the tubular goods. These types of external corrosion are typically controlled by disrupting the electrical circuits with insulating couplings and by cathodic protection.
Many types of insulating couplings have been proposed; but most are either unreliable for high pressure use or are hard to test because of the alternate resistance paths around the coupling. Moreover, most involve metal portions which are very close to each other and the insulated space between the metal parts is easily shorted by debris and the products of corrosion. It would, therefore, be desirable to provide a more reliable high pressure electrical insulator, especially one that provides greater separation between exposed metal parts.